Controlling friction atom by atom

Friction is a phenomenon of great technological relevance. The empirical laws of friction date back to the investigations of Leonardo da Vinci (1452 to 1519) and Guillaume Amontons (1663 to 1705). Thus, we have known for a long time that friction is proportional to the force normal to a surface and independent of the geometrical contact area. We also know that friction is one of major sources of energy loss, whereby a large amount of energy is dissipated into heat. In some cases, suitable surface preparation can lead to superlubricity, which corresponds to a state with extremely low frictional forces, where energy dissipation is at a minimum (1). On page 1115 of this issue, Bylinskii et al. (2) describe a cold-atom system that takes us to the ultimate limit of friction. They show that a defined number of ions, from one to six, can be moved across an optical lattice to study the elementary processes of atomic friction.